No abstract

The aim of the current paper is to decrease the required computational time and memory of the direct simulation Monte Carlo (DSMC) method using the simplified Bernoulli-trials (SBT) collision algorithm in combination with the transient adaptive subcell (TAS) technique. It is already shown that SBT collision could provide accurate solutions with a few particles per cell, when the requirement for grid resolution of the pure SBT remains the same as standard DSMC collision algorithms. Here, we demonstrate that the combination of the SBT with the TAS technique could reduce the number of required cells considerably, especially for low Kn micro/nano flows, while the accuracy is preserved and computational time decreases. The efficiency of the SBT-TAS is investigated for two typical test cases, i.e., low Knudsen/low speed flow in micro cavity and high speed/high gradient flow over the nano-scale flat plate. We tested cavity flow at Kn=0.005 and show that SBT-TAS solution using a coarse grid of 50×50 agrees suitably with the NTC solution using a 200×200 cell with 2×2 fixed subcells and number of particles per cell PPC=20 (called correct solution), see Fig. 4, while the computational time of the SBT-TAS decreases by 64%. We show that using of TAS grid movement (SBT-TAS-Dual) decreases the mean collision separation; however, accuracy gain is almost slight compared to the extra computational cost of the grid movement. We will show that product of the local Knudsen number by the average subcells number in a cell is constant. For flow over the flat plate geometry, we will show that even though TAS scheme could provide enough number of collision subcells even for quite coarse grids, the smearing of gradients due to larger sample cell size could deteriorate the final solution.

Using the stones to make tools and vessels dated back to Paleolithic and Neolithic periods. Stones so called soft stones, along with the alabaster, are one of the most famous stones that have been used to produce vessel in Near East, where they are in use currently in different applications. Soft stone vessels reach to highest level of flourishing during the Bronze Age and its geographical exchange area stretches from India in east to Syria in west. Iran, as one of the most important places of this kind of stones, was a potentially center in this trade and archaeological sites such as Tape Yahya and Konar Sandal in Kerman province are some of the most famous sites in making and exporting this kind of objects. Although soft stone vessel making continued during historical to Islamic era, but this industry has been neglected by researchers and archaeologist. In addition, until now morphological and artistic reports and archaeometry studies have focused only on Bronze Age vessels. During six seasons archaeological excavations at an Islamic Archaeological site called Shadyakh near to modern city of Neyshabur (about 2 km south east of Neyshabur), which its date goes back to Early and middle Islamic period, many cultural objects, like the pottery, glass, metal, bones, human skeletal, plaster, and architectural remains have been discovered. Beside of these samples, several pieces of soft stone vessels were discovered from several archaeological excavations. No evidence of workshop or crafting was reported and according to geological reports around this region, no outcrop of soft stone was seen. Although that these vessels are important, no study have yet been conducted on them. At this research, the vessels have been archaeometrically studied. The main objective of this research was to gain the information about the structural characteristics of soft stone vessels recovered from this site. Before this, Kohl and his collogues in 1979 carried an investigation on large amount of Bronze Age archaeological samples from Middle East. They found several main groups and a mine around Mashhad was recognized. Other researches on soft stones include Razani's M.A and Imami and his colleague's researches on new chlorite mines of Ashin; and Afshari Nezhad and Razani's research on structural characterization and conservation of Jiroft cultural basin's chlorite vessels. The only research on historical and Islamic soft stone vessels was about the effect of cooking conditions on structure of vessels. At this research, totally 16 samples from different seasons of archaeological excavations of Shadyakh were collected and analyzed by XRD, 4 sample analyzed by XRF, and 2 samples by SEM. The results of XRD analysis showed two main groups, while 21 trace elements and 11 chemical compound were detected by XRF. The raw data was studied by Excel statistic software. At this study, overlap graph was prepared according to finding difference or similarity between samples where the results show high similarity among the samples. The SEM and XRD results ...